Dump trucks or so-called large dump trucks are predominantly used in coal mining operations or ore mining operations for the transport of the mined coal, minerals and ores. These bulk material dumpers are manufactured in sizes of more than 90 metric tons (t) up to several 100 t in weight and payload so that they have very large dimensions overall.
A diesel electric drive is used as the traction drive, wherein the mechanical energy generated by a diesel engine is converted with the aid of a generator into electrical energy for the supply of the electric traction drives. The reason for this process is that diesel engines, like all internal combustion engines, can only be operated with ideal efficiency in a very restricted speed range and cannot be started under load. The AC motors for the driving axle which are used can also produce the desired torque in the lower speed range for starting. The internal combustion engine used can be operated continuously in the ideal speed range.
Various components of the fraction drive requiring cooling were previously cooled by means of separate cooling systems, which results in a not insubstantial effort in the production of such dump trucks caused by the construction.
To make matters worse, the cooler inlet of the mobile work machine is typically seated in the region of the vehicle front, but the components to be cooled in the diesel electric drives used are rather arranged in the rear region. The transmission oil to be cooled is currently conducted from the vehicle rear in the direction of the heat exchangers mounted at the vehicle front to utilize the cooling effect of the air stream. This would mean that hot oil is disadvantageously conducted past the combustion engine, whereby a huge risk of fire results.
It is the object of the present disclosure to provide an improved cooling system of a mobile work machine of the category.
This object is achieved by a mobile work machine, in particular by a dump truck or by a truck, having a common cooling circuit comprising a liquid cooling medium for the parallel cooling of one or more components of the power electronics of the diesel electric drive and for the cooling of one or more drive components in the region of the driven vehicle axle. The required circulation path of the liquid cooling medium is reduced to a minimum by the use of a common cooling circuit. An effective cooling effect can be achieved by the shortened flow paths. At the same time, the total complexity of the work machine is reduced since no separate cooling systems have to be provided and serviced.
Water or glycol can be considered as the used cooling medium, for example.
The one or more components of the driven vehicle axle to be driven are, for example, one or more electrical drive motors of the diesel electric drive which, for example, drive the tires of the driven axle in pairs. The rear axle is typically the driven axle of the mobile work machine.
It is conceivable that the electrical drive motors drive their associated axial section or the wheel hubs of the driven vehicle axle in a speed transformed manner via suitable transmissions 75. The transmission oil used can likewise be coolable by the common cooling circuit. One or more planetary transmissions which are each integrated into the wheel hubs and which transfer the output moment of the electric motors to the wheel axle or wheel hub are frequently used as such transmissions.
The cooling of the transmission oil can be realized by means of one or more oil coolant heat exchangers. The required heat exchangers are, for example, arranged close to the transmission to keep the line path of the transmission oil as short as possible. An arrangement is conceivable in the region of the driven vehicle axle or in the region between the driven axle and the power electronics or, optionally, in the region between the generator and the power electronics. Cooling liquid of the common cooling circuit thus flows through the electric motors used, on the one hand, and through the one or more transmissions, in particular planetary transmissions, i.e. the heat exchangers used, on the other hand.
The advantageous arrangement of the heat exchangers makes a supply of the hot transmission oil from the driven rear axle up to the front region of the vehicle superfluous; the risk that the conveyed oil ignites is reduced.
One or more of the components of the power electronics to be cooled are, for example, one or more frequency converters for controlling the one or more electric motors of the driven vehicle axle. The generator of the diesel electric drive used is also understood as a component to be cooled in this connection. The one or more components of the power electronics are flowed through by the cooling liquid of the common cooling circuit in a known manner and are effectively cooled down.
The circulation may take place within the coolant circuit such that components having a higher cooling requirement are cooled or flowed through with priority, whereas components having a smaller cooling requirement are arranged downstream in the cooling circuit. The components of the power electronics, for example, have to be cooled down a lot more or require a lower temperature of the coolant since the regular operating temperature of the component is lower.
The transmission oil used of the one or more transmissions to be cooled is, in contrast, less demanding and less in need of cooling so that the temperature of the coolant can be higher for a sufficient cooling. It is proposed for this reason in accordance with an advantageous embodiment of the present disclosure that the cooling medium of the common cooling circuit first cools or flows through those components of the power electronics, such as the frequency converters, and/or the electric motors of the driven axle and is supplied subordinately to the one or more heat exchangers for cooling the transmission oil of the transmission types used in the driven vehicle axle.
The common coolant circuit is optionally configured such that at least some of the components to be cooled having similar cooling demands are cooled or flowed through in parallel. Provision can be made, for example, that the components of the power electronics and/or at least one of the electric drive motors is/are cooled or flowed through in parallel by the cooling medium of the common cooling circuit, whereas the one or more transmissions of the driven vehicle axle are cooled or flowed through subordinately.
In an example embodiment of the present disclosure, the cooling medium is conducted through a liquid cooler arranged as a heat sink in the front region of the work machine and is led from there via one or more pumps in the direction of the components to be cooled in the rear region.
Further advantages and properties of the present disclosure result from the embodiment shown in the Figures.